Discharge device



July 2, 1935. N, H. STEWART DISCHARGE DEVICE Filed Sept. 50, 1955INVENTOR /v. H. Tfn/AFT BY7 71 n ATTORNEY iff Patented July 2, 1935DISCHARGE DEYICE Nelson f H. Stewart,y Verona,l `N. J., assignor toWestinghouse Lamp Company, a corporation of Pennsylvania ApplicationSeptember 30, 1933, Serial No. 691,575

v 1 claim. (ol. 25o- 35) :This invention relates toelectric discharge"devices and more particularly to devices of this character employed"inthe X-rayfield and commonly termed .X-'ray tubes.

l5 cific aspect the invention is directed to an improved construction inX-ray tubes of the type disclosed inthe VUnited Statespatent toNelson H.Stewart-which patent Was 'issued on August 1,1933 and bears thenumber1,920,606. f

ing an elongated envelope having an anode, a cathode ,and an `Xrayscreening means Ytherein. rThescreen houses the target end of the.

anode .and lthe cathode to screen o-ut undesirable X-rays. The screen'is composed of nickel-iron and is relatively heavy.v Because-oftheweight of thefscreenit has'been necessary toprovide means for supportingthe same within the tube. Heretofore, for this purpose, it has beenpro-r posed to employ ka plurality of plates and conducting Wires. Theconducting wires'A served to aid in the supporting of the screen as wellas providing a conductingpath for the current to be supplied to thecathode. These wires-were sealeddirectly in said envelope, forming aglassto-metall Wireseal and vextended exteriorly and interiorlyof Asaidenvelope. The interior pore tionsof said 'wires were mechanicallyconnected to saidscreen and 'electrically connected tothe cathode.,

Was nota commercially feasible construction because the entire weight ofthe screen is carried by 'the seals. In normal Vtransportatio'n and whensubjected rto the shocks incident to manipulation andoperationthesealssometimes fractured because the glass was strained atthe seals. In order to prevent said screen from striking the side wallrof the envelope there are provided a' plurality of resilient plateslocated betweenr the screen and envelope. So that the screen might notbe totally supported bysaid seals and by the frictional engagement ofsaid screen andenvelope with the resilient plates, at least one of theplates has an vupstanding ear with an opening therein throughWhich'projects a ynipple on the interiorl of said envelope. Theresilient plate, Whose ear surrounds said nipple, supports said plate tomaintain the screen from sliding longitudinally in said tube.

, Although' Vthe aforesaidy arrangement has served the purpose ofsupporting the screen, tubes of this construction have not always beensatisfactory for other reasons and, in addition, manufacturingdifficulties were encountered in production. q Generally, the nipple.'is formed by merely heating the evacuated bulb, .containingy theinternal parts, at afrestricted area just opposite the opening in theear of the resilient f plate. 'In some casesjthe glass is heated too Inits more spe-y Said-patentdiscloses an X-rayY tube compris-` The'screen, solely Ysupported Aby, said wires,

highly'at this area or,'fo'r some other reason,

the heated glass is drawn inandV bubblessothat.`

it is readily pierced. Even when the nipple'is properly formed, thatportion of the glass which. has been heated has its internal structure"changed. As a consequence itiisv strainedfat that point*` and may crackupon cooling 'or .in u

normal manipulation, transportation or operation. Of course annealingthev glass after the nipple is formed suggests itself as a solution,"

but it is not commercially feasible becauseit is too diicult to carryout when the nipple hasta,

vacuum on one side. l

In order to eliminate these physical shortcom` ings inherent in thetubes heretofore manufac-' tured, I have developedthe followinginvention. Briefly stated, the invention comprises the elimination of aWire-to-glassfseal to support the screen and also the elimination of thevitreous teat or nipple for supporting the screen. For this purpose, Iemploy one or more copper thimbles ring-sealed tolthe envelope andconnected to said screen for supportingthefsame.

An object of my invention is to provide an electric discharge devicewhose heavy elements are supported by a ring seal to renderv them morerugged and so that shrinkage during manufacturing is considerablyreduced. Q

Another object of my inventionv is to provide an electric dischargedevice containing no glass-'-v to-wire seals, but onlyring seals.

Another object of my invention is to` provide an X-ray tube that is more`rugged than those heretofore produced. Y

VA still further object of my "invention is to provide an'X-ray tubeWhose Yheavy screen'issupported by a ring seal. f

These and other objects of my invention may bereadily ascertainedfromthe following speci-l iicationA and drawing wherein,

Figure `1 represents a longitudinal cross sectional view With some ofthe parts inl elevation having a body'portion Ilv of generallycylindricalv form with a hemispherical portion l2 atone end and areentrant tube I 3V at its other end. vr'This ree'ntrarit tube I3extends upwardly into'the lbody portion, and has a copper sleeve `orsup"-r` port coupling I4 Vhermeticallyv sealed thereto. An anodeextension-I5 is secured toand'car?v ried by: said coupling I4. An anodeI6` is locat-.V ed within -the envelope :and-is also?v carried ,by

said support coupling I4. Intermediate the lower end of the anode I6 andthe coupling I4 is a thimble shield II whose lower end extends below theseal between the coupling I4 and the reentrant tube I3.

Fusedly ring-sealed to the inner wall of the envelope I0 is a vitreoustubular cylinder I8 extending upwardly in the envelope. ode I6 issurrounded by said cylinder or sleeve I8. A plurality of resilientplates I9 bear against the outer surface of the anode and the innersurface of the sleeve I8 to partially support the anode and to absorbmechanical shocks.

Disposed around and having its interior wall spaced from the free end ofthe anode I6 is an X-ray screen composed of nickel-iron and consistingof a cylindrical portion 20 and a top plate 22 secured to each other inany convement manner. The X-ray screen houses the free end of the anodeand a cathode 23 together with its'focusing cup 24.

According to my invention I provide a novel means for supporting saidscreen, which means may also serve as the conductors of electricity forthe cathode 23. My novel means comprises essentially the employment of acap or thimble having its free circular edge ring-sealed by fusion to asmall cylindrical section extending from the wall ofthe envelope. Thistype of construction permits the construction of more rugged X-ray tubesand also lowers the manufacturing costs because it reduces thepercentage of tubes whose envelopes had to be discarded and the partsreassembled when the old type of support was employed.

In carrying out my invention, the upper end of the 'cylindrical portionII of the envelope has a pair of diametrically disposed short outwardlyextending small cylindrical vitreous sleeves 25 and 26. United to theouter ends of said sleeves 25 and 26 by fusion are, respectively, shortreentrant vitreous tubular sleeves 2'| and 28. The free ends of thesesleeves 2'I Vand 28 are spaced l a slight distance from the inner wallsof the sleeves 25 and 26. `A thimble or cap 29 composed of copper or thelike is secured to each of said sleeves 21 and 28 and to the X-rayscreen to properly support the latter.

As illustrated, the thimbles or caps 29 may be of any desired shape. Therims of the caps or thimbles 29 are tapered downwardly towards the freeedges. The caps 29 are secured to the short tubular sleeves 21 and 28 bya simple fusion process so that the joint between the glass and metalshall be a hermetic and air-tight seal. Integrally united to the base ofthe caps 29 are conducting rods 30 and 3| which may be of the samecomposition as the cap per se. The rods 30 extend outwardly from saidcaps and the rods 3I are located within said envelope.

A cap, having rods 30 and 3 I, may be machined out of a single piece ofmetal. The outer or free ends of the rods 3| are threaded. Inverted J-shaped rigid supports 33 and 34 are secured onto the inner rods 3 I.'Ihe outer portion of the elongated arms of the members 33 and 34 arealso screw threaded. The screw threaded portion of the rod 34 isthreadedly secured to a threaded opening 35 in the top plate of theX-ray screen member.

An opening diametrically disposed with relation-to the opening 35 has aninsulating bushing 36.1ocated therein. Passing through said bushingwhich insulates the same from the X-ray The ani screen member is thethreaded portion of the rod 33. A nut 3'I is screwed onto each of theoutermost ends of the rods 33 and 34. The outer ends of the cathode 23are secured to the outer ends of the rods 33 and 34. 'Ihus the rods 33Vand 34 act as supports for both the screen member and the cathode.

In order that the entire weight of the X-ray screen member Yneed not becarried by the caps 29 and also in order that the tube shall be furtherprotected from mechanical shocks, I provide a plurality of spacedresilient plates 39. These plates 39 are of the type disclosed by A. C.Blakeman in his copending application Serial No. 560,738 filed September2, 1931 and assigned to the same assignee as the present invention. Theplates 39 are spaced around the screen land bear against the outersurface of the screen'and the inner wall of the envelope.V With myconstruction and especially because I use the thimbles or caps 29, Ineed not employ a resilient plate having an upstanding ear with anopening therein tting around a vitreous nipple in the envelope. As amatter of fact with the construction shown in Figure l, it is notnecessary that I employ a resilient plate having an upstanding ear.

However, it is within the purview of my invention to employ a resilientplate having an upstandjng ear. Sometimes I may desire to substitute aflexible member for the members 33 and 34. When this is a prerequisiteor desirable, I employ a structurev such as shown in Figure 2. For themembers 33 and 34 shown in Figure l, I may substitute flexible memberssuch as 40, secured respectively to the rods 38 and 3| and associatedwith the screen in the same manner as the rods 33 and 34. One of theresilient plates 39 may have an ear 42 with its opening fitting over therod 3| to prevent excess longitudinal displacement of said screen. If Idesire, I may have an ear on each of two resilient plates, with theopenings in said ears fitting respectively over the rods 30 and 3| andmounted on an insulator 43, as shown. Contact caps 44 t over theoutwardly extending vitreous sleeves and are sealed with a basing cement45 and soldered to the outwardly extending rods 30.

Although I have described my invention withI some particularity it isnot to be limited to the exact construction shown and described, butonly by the prior art.

What is claimed is:

An X-ray tube comprising an elongated vitreous-envelope, an anode, acathode and an X-ray screen therein, said envelope consisting of a bodyportion, a reentrant tube in the lower end of said body portion, ahemispherical portion at the upper end of said body portion, a pair ofdiametrically opposed vitreous tubular sections integral with said bodyportion and extending therefrom, a short reentrant vitreous tubeintegral with each section, a plurality of metallic caps carried by saidreentrant tubes, each of said reentrant tubes having one of said capsring-sealed thereto, said anode electrically connected to one of saidcaps, a cathode electrically connected to said other caps, meansconnected to said screen and one of said caps for supporting saidscreen, and a plurality of resilient plates bearing against the outersurface of said screen and the inner surface of said envelope to alsosupport said screen and protect the envelope from mechanical shocks.

NELSON H. STEWART. i

